Syringe

ABSTRACT

A syringe for administering a medicament having a barrel provided with a needle attachment member to which a needle may be mounted and which is retained by a catch at one end of the barrel, and a plunger which is movable in the barrel to expel medicament through the needle attachment member and needle. The plunger is hollow and contains a vacuum and is provided with a gripping member at one end which closes one end of the plunger and which when the plunger is advanced can engage the needle attachment member to releases its catch and withdraw the needle attachment member and mounted needle into the plunger.

FIELD OF THE INVENTION

This invention relates to a safety syringe and in particular to a singleuse syringe having provision for retraction of a hypodermic needle intothe body of the syringe.

BACKGROUND ART

With the advent of contagious diseases such as AIDS and Hepatitis B, thepossibility of so called "needle stick" injuries in the medicalenvironment has proliferated along with many and varied arrangements forpreventing accidental infection of medical workers as a result of thistype of injury. In addition, the proliferation of intravenous drug usehas resulted in discarded syringes and needles on beaches and otherareas where a passer-by can inadvertently step on a needle and also beinfected.

As a result of this, there has been a proliferation of proposals forsingle use disposable syringes whereby a needle is retracted into thebody of the syringe after a single use. However, most of thesearrangements involve complete reworking of the conventional disposablesyringe construction in such a way that the conventional luer lockdisposable needle fitments are done away with such that the arrangementsproposed are too complex and too expensive. Many also require additionalmanual steps to retract the needle.

A typical example of the prior art is U.S. Pat. No. 4,995,870 whichdescribes a safety syringe where the needle bas a barb on the end insidethe syringe for engaging the syringe plunger when the plunger isdepressed to inject its contents into a patient. Once the barb engagesthe plunger the operator unlocks the needle and then withdraws theplunger to retract the needle into the syringe. The needle used is not aconventional luer lock fitment as it must have a barb on the end and theretraction process requires two manual steps which expose the operatorof the syringe to the risk of "needle stick" injuries and aretime-consuming and inconvenient.

A number of automatically retracting syringes have therefore beenproposed. These include spring-loaded devices such as that described inU.S. Pat. No. 4,929,237 where a pushing force applied to the proximalend of the syringe moves the syringe within a housing against a springto an operative position and releasing the pushing force allows thesyringe to retract proximally drawing the needle back into the housing.The syringe is complex and likely to be expensive.

Australian Application No. 66,363/90 discloses a syringe where theplunger captures the needle and the plunger is withdrawn by a returnspring when the downward pressure on it is released, thereby retractingthe needle. The specification at page 6, line 22 refers to withdrawingthe entire plunger and the attached needle back into the barrel of thesyringe using a vacuum, but proposes no feasible way to do this. Theonly embodiments described use a return spring and the snap lockengagement means used to secure the needle to the plunger leaves a verylarge space (best seen in FIG. 3) in which medicament will remain whenthe plunger is withdrawn. The medicament is then likely to leak,creating a contamination hazard.

A vacuum-retractable syringe is proposed in Australian Application No.70,672/91 where the needle is withdrawn into the interior of a hollowplunger under force of a vacuum within the plunger, however, in thatinvention the thrust exerted by the operator of the syringe must besufficient to cause a washer at the end of travel of the plunger torupture and to push a plug down through the washer to engage the needle.The needle mount (which is not a conventional luer lock) must alsorupture so that the plug can withdraw the needle under vacuum into theplunger, where it is held in place by magnets. The syringe iscomplicated and unlikely to be feasible due to its complex operation.

These proposals have not found ready acceptance in the medicalprofession because of cost and inconvenience.

DISCLOSURE OF THE INVENTION

According to the present invention there is provided a syringe foradministering medicaments comprising:

an elongate barrel for holding the medicament having a proximal anddistal end;

a hollow plunger having a closed proximal end protruding from theproximal end of the barrel and a distal end located within the barrel,said plunger being slidably mounted in said barrel and having vacuummeans in its interior;

a retractable needle attachment member adapted to receive a hypodermicneedle contiguous with the distal end of said barrel and so arrangedthat operation of said plunger causes medicament to be expelled fromwithin said barrel through the hypodermic needle; and

needle attachment member gripping means constituting a closure of thedistal end of said plunger and being adapted to engage the needleattachment member so that the needle attachment member can be retractedinto the interior of said plunger by the vacuum within said plunger.

The retractable needle attachment member preferably protrudes from thedistal end of the barrel into a retaining shoulder attached to thebarrel and has a portion adapted so that a conventional luer lockhypodermic needle can be releasably attached to the syringe andmedicament can be expelled through the retractable needle attachmentmember and through the needle as the plunger as forced toward the distalend of the barrel.

Advantageously, the needle attachment member is operatively secured inthe retaining shoulder and therefore to the distal end of the barrel bya releasable catch which is released when the plunger as pushed home toexpel the contents of the syringe through the hypodermic needle. Thecatch preferably comprises an annular shoulder on an internal wall ofthe retaining shoulder adjacent the distal end of the barrel whichco-operates with an outwardly biased finger protruding from a side wallof the needle attachment member. Advantageously, as a consequence of theengagement between the annular shoulder and the biased finger, theneedle attachment member is biased into sealing engagement with thebarrel at longitudinally spaced sealing sites while the retractableneedle attachment member is a slide fit rather than a friction fit inthe distal end of the barrel.

It is particularly preferred that the biased finger includes aprotrusion that engages the annular shoulder and a portion of reducedthickness distally adjacent the protrusion constituting a pivot pointfor the biased finger so that the biased finger bends outwardlymaintaining the engagement of the projection with the annular shoulderwhen the needle attachment means is subject to force in the proximaldirection. A significant force in the proximal direction is generatedwhen the needle of a syringe is pushed into the patient. When the pivotpoint of the biased finger is located adjacent the projection this forceserves to hold the needle attachment member more tightly in theretaining shoulder but, if it were spaced further from the projectionwould tend to cause the needle attachment means to dislodge.

The retractable needle attachment member gripping means preferablyreleases the needle attachment member when the plunger is pushed home sothat it can be drawn back into the syringe along with the exposedneedle. Advantageously, the gripping means includes a catch releasemechanism adapted to engage the biased finger on the needle attachmentmember and release the biased finger from engagement with the annularshoulder so that the needle attachment means engages the gripping meansand is released from the retaining shoulder, whereby the gripping meansdisengages from the distal end of the plunger and the gripping means inoperative engagement with the needle attachment means is retracted intothe interior of said plunger by the vacuum within said plunger.Preferably, the catch release mechanism comprises a claw memberincluding a leading camming surface and a trailing shoulder, thetrailing shoulder being adapted to engage the distal face of the plungerand the camming surface being adapted to abut an inside surface of theretaining shoulder, whereby the claw member is urged to bend inwardlywith the camming surface engaging the biased finger and the trailingshoulder disengaging the distal face of the plunger.

If the vacuum fails for some reason to retract the needle, it ispreferred that the syringe be arranged so that the needle can beretracted manually by retracting the plunger. Preferably, the grippingmeans includes first annular beading adjacent its proximal end and theplunger includes second annular beading on its inside surface adjacentthe distal end of the plunger, wherein on manual withdrawal of theplunger in the proximal direction the second annular beading on theplunger engages the first annular beading on the gripping means allowingthe gripping means and operatively engaged needle attachment means to bewithdrawn into the barrel in the event that the vacuum retraction fails.

A further safety feature of the present invention is that the syringecover may be adapted to close the opening left by retraction of theneedle attachment member.

BRIEF DESCRIPTION OF THE DRAWINGS

In order that the present invention can be more readily understood andbe put into practical effect, reference will now be made to theaccompanying drawings and wherein:

FIG. 1 is a perspective view of a syringe in accordance with oneembodiment of the invention,

FIG. 2 a view similar to FIG. 1 showing the needle in the retractedposition after use,

FIGS. 3 to 8 are partial longitudinal cross-sectional views through thedistal end of the barrel of the syringe shown in FIGS. 1 and 2 (withouta needle) illustrating the steps in the retraction process,

FIG. 9 is a longitudinal cross-sectional view of the syringe shown inFIGS. 1 and 2 illustrating the use of the protective cap to close theopening in a used syringe, and,

FIG. 10 as a view similar to FIG. 3 showing the action of the lockingprojections in response to a resistive force of the skin of the user atthe start of the injection process.

DESCRIPTION OF THE PREFERRED EMBODIMENT

As seen in FIG. 1, the syringe 10 comprises a hollow evacuated plunger11 slidably mounted within an elongated barrel 12 which as a proximalend 13 and a distal end 14. The hollow plunger 11 has a proximal end 15protruding from the proximal end 13 of the barrel 12 and a distal end 16axially slidable within the barrel 12. The plunger 11 (or at least at aportion of it towards its distal end) is hollow and a chamber 25 insideplunger 11 as evacuated so that there is a vacuum inside the plunger.The barrel 12 has a flange 17 at its proximal end 13 that is gripped bythe operator when using the syringe 10. At its distal end 14, the barrel12 has a retaining shoulder 18 which retains the needle attachmentmember 26. The hypodermic needle 20 has a lock 19 by means of which theneedle is attached to the member 26 and the arrangement is preferably aconventional luer lock hypodermic needle. The needle 20 is covered byprotective cover 21 until just prior to use so that accidental punctureinjuries cannot occur.

The syringe 10 in FIG. 1 is shown with cover 21 partially removed. Whenthe cover 21 is removed, plunger 11 is pulled back in the direction ofarrow A to draw a medicament (not shown) through needle 20 into thespace 24 in the barrel 12. The barrel 12 (which may have a graduatedvolume scale marked thereon) is about half full in FIG. 1. Furthermovement of the plunger 11 in the direction of arrow A will continue thefilling of the barrel 12 and, once the desired volume of medicament hasbeen drawn into the barrel 12 and needle 20 has been inserted into apatient, the medicament can be expelled by depressing the plunger in thedirection opposite to arrow A.

FIG. 2 shows syringe 10 after the medicament has been injected into apatient. The needle 20 and locking element 19 are withdrawn intoevacuated chamber 23 in the plunger 11 by the action of the vacuumwithin the plunger (the process by which this occurs will be describedbelow in relation to FIGS. 3 to 8). Protective cover 21 is then insertedinto the opening 22 through which locking element 19 previouslyprotruded to close off the opening. This extra security feature isbetter illustrated in FIG. 9. The protective cover 21 is shaped andproportioned so that it will sit tightly over locking element 19 andremain in place over the needle 20 prior to use but will also fittightly into opening 22 when that is created after use of the syringe toseal that opening.

FIG. 3 shows the final stage of the injection process where the distalend 16 of the plunger 11 approaches the distal end 14 of the barrel 12.The space 24 (containing the 25 medicament) within the barrel 12 is verysmall as most of the medicament has been injected into the patientthrough the needle 20. Retractable needle attachment member 26 has acoupling portion 26a to which the locking element 19 (here aconventional luer lock) is attached in the conventional manner is alsoshown. Gripping means 25 which are adapted to engage needle attachmentmember 26 are located at the distal end 16 of the plunger 11 andconstitute the closure of evacuated chamber 23 therein. "O" rings 39 arefitted around the distal end 16 of the plunger 11.

As shown in FIG. 4, as gripping means 25 approaches needle attachmentmember 26, claw member 27 (which is one of a plurality ofcircumferentially spaced claw members on gripping means 25) abuts finger28 (which is one of a plurality of circumferentially spaced fingers onneedle attachment member 26). Each claw member 27 has a leading cammingsurface 32 and a trailing shoulder 33. The trailing shoulder 33 engagesthe distal face 35 of the plunger 11 so that as the plunger is pushed inthe distal direction to expel the medicament, the gripping means 25travels with it in the distal direction until the camming surface 32abuts the surface 34 on the inside of the retaining shoulder 18.

The action of claw member 27 on finger 28 pushes it inwardly against themain portion of needle attachment member 26. As force in the distaldirection is maintained on the plunger 11, claw member 27 starts to movepast finger 28. This is best seen in FIG. 5.

Each of the circumferential fingers 28 is outwardly biased and has alocking projection 29 thereon which engages with an annular shoulder 30on retaining shoulder 18. Retaining shoulder 18 is simply a mouldedextension of barrel 12 therefore this effectively holds the needleattachment member 26 at the distal end 14 of barrel 12 so thatmedicament may be delivered from the space 24 in the barrel 12 through abore in needle attachment member 26 into the needle 20 and thence intothe patient. An O-ring 31 provides a seal around the needle attachmentmember 26 to prevent leakage of the medicament from the barrel 12.

Referring to FIGS. 5 and 6, it can be seen that with further movement ofthe plunger 11 in the distal direction (to fully discharge the contentsof the syringe) the camming surface 32 of claw member 27 abuts surface34 which causes the claw member 27 to bend inwardly. This results in theend of the claw member 27 engaging finger 28 on the needle attachmentmember 26 and in projection 29 fully disengaging shoulder 30 on theretaining shoulder 18. The needle attachment is, therefore, no longeranchored to the barrel 12. but is attached to the gripping means 25which form the distal closure of evacuated chamber 23. Since the inwardbending of claw member 27 also disengages trailing shoulder 33 from thedistal face 35 of the plunger 11, the gripping means 25 is drawn by thevacuum in the direction of arrow B into the evacuated chamber 23 in theplunger 11. As the needle attachment means 26 now engages the grippingmeans 25, it and the needle 20 attached thereto by locking element 19are also drawn into the evacuated chamber 23 in the plunger 11. FIG. 8illustrates the needle 20 as it is retracting and reference once againto FIG. 2 shows the final position of the needle 20.

In order to maintain a suitable vacuum in the chamber 23, it ispreferred that the plunger 11 be made of a polymeric material capable ofholding a vacuum for a long period, such as polyethylene terephthalate(PET). Alternatively, the plunger may be made of a material such aspolypropylene or other conventional materials which will hold a vacuumfor 3 to 5 days. If the latter materials are used it is preferred topack the syringe in a barrier bag which will maintain a vacuum for along period in and around the syringe. Suitable bags are well known tothose skilled in the art.

The walls of chamber 23 (the interior walls of plunger 11) say beequipped with annular beading (not shown) to engage the annular beading36 on the gripping means 25 to hold the retracted gripping means and theneedle attached thereto in position within the plunger 11.Alternatively, the arrangement illustrated in FIG. 9 where theprotective cap 21 is jammed into opening 22 covering the needle 20within the chamber 23 and preventing it from moving in such a way thatit could protrude from the opening 22 may be used.

The mechanism illustrated in FIGS. 3 to 8 may also be used in larger orsmaller syringes than the syringe illustrated and in syringes where theretaining shoulder is off centre using the same size needle attachmentmeans (but varying the size and/or shape of the gripping means) so thata standard needle can always be used.

The plunger 11 may optionally be equipped with annular beading 37 sothat should the vacuum fail the beading 37 and the beading 36 on thegripping means 25 will engage on manual retraction of the plunger sothat the needle 20 can be retracted manually into the barrel 12. This isa useful back-up system and provides an additional security feature.

FIG. 10 shows the action of the locking projections 29 in response tothe resistive force of the skin in the direction of arrow C. The pivotpoint 42 is close to the locking projections 29 so that the longitudinalload in the direction of arrow C forces the locking projections 29outwards rather than inwards. The needle 20 has been omitted for thesake of clarity.

It will be appreciated from the foregoing that the present inventionprovides a safety syringe which is simple and cheap to manufacture andwhich can be equipped with a needle attachment member having the normalluer lock fitment and hence, can be used in place of a conventionalhypodermic syringe. There are no manual steps necessary to retract theneedle so operation of the syringe is no more difficult ortime-consuming than a conventional syringe. Furthermore, sinceretraction of the needle is automatic once the contents of the syringehave been expelled the operator is not exposed to the risk of punctureinjuries by the used needle and the needle cannot be used again. Thisgreatly reduces the risk of accidentally contracting diseases from theinfected blood of a patient.

It will also be appreciated that while a specific form of the inventionhas been discussed above by way of illustrative example of the presentinvention, many other variations and modifications thereto will beapparent to those skilled in the art without departing from the broadambit and scope of the invention as defined in the appended claims.

I claim:
 1. A syringe for administering medicaments comprising:anelongated barrel for holding a said medicament, said barrel having aproximal end and distal end; a hollow plunger having a closed proximalend protruding from the proximal end of said barrel and a distal endlocated within said barrel, said plunger being slidably mounted in saidbarrel and having vacuum means in its interior; a retractable needleattachment member for supporting a hypodermic needle, said needleattachment member including releasable retaining means cooperable withmeans on said barrel to retain said needle attachment member at saiddistal end of said barrel; gripping means for gripping and withdrawingsaid needle attachment member into said plunger, said gripping meansclosing said distal end of said plunger, said gripping means cooperatingwith said distal end of said plunger so that said gripping means isretained at said distal end of said plunger; and abutment means withinsaid barrel in the path of movement of said gripping means, saidabutment means being engageable by said gripping means upon apredetermined movement of said plunger towards said needle attachmentmember, said engagement causing said gripping means to be reduced inradial dimensions so as to be disengaged from said distal end of saidplunger, said abutment means further urging said gripping means intoengagement with said retaining means of said needle attachment membersuch that said gripping means grips said retaining means and caused saidretaining means to release said needle attachment member from engagementwith said barrel to permit said needle attachment member to be withdrawnby said gripping means into the interior of said plunger by the vacuumwithin said plunger.
 2. A syringe according to claim 1 wherein saidneedle attachment member is located in a retaining shoulder whichprotrudes from said distal end of said barrel and includes a portion forreleasable attachment of a luer lock hypodermic needle wherebymedicament can be expelled through said needle attachment member andthence through said needle as said plunger moves toward said distal endof said barrel.
 3. A syringe according to claim 2 wherein said needleattachment member is operatively secured in said retaining shoulder bysaid releasable retaining means which comprises a releasable catch whichis released when said plunger is pushed home to expel substantially saidmedicament from said barrel through said needle.
 4. A syringe accordingto claim 3 wherein said catch further comprises an annular shoulder onan internal wall of said retaining shoulder which cooperates with anoutwardly biased finger protruding from a side wall of said needleattachment member, said outwardly biased finger comprising saidreleasable retaining means.
 5. A syringe according to claim 4 whereinsaid biased finger includes a protrusion that engages said annularshoulder and a portion of reduced thickness distally adjacent saidprotrusion constituting a pivot point for said biased finger so thatsaid biased finger bends outwardly maintaining the engagement of saidprojection with said needle attachment means is subject to force in theproximal direction.
 6. A syringe according to claim 4 wherein saidgripping means includes a catch release mechanism adapted to engage saidbiased finger on said needle attachment member and release said biasedfinger from engagement with said annular shoulder so that said needleattachment member engages said gripping means and is released from saidretaining shoulder, whereby said gripping means disengages from saiddistal end of said plunger and said gripping means in operativeengagement with said needle attachment member is retracted into theinterior of said plunger by the vacuum within said plunger.
 7. A syringeaccording to claim 6 wherein said catch release mechanism comprises aclaw member including a leading camming surface said shoulder, saidtrailing shoulder normally engaging a distal face of said plunger andsaid camming surface being adapted to abut an inside surface of saidretaining shoulder, whereby said claw member is urged to bend inwardlywhen said camming surface abuts said retaining shoulder inside surfaceto engage said biased finger and causing said trailing shoulder todisengage from said distal face of said plunger.
 8. A syringe accordingto claim 1 wherein said gripping means includes a first annular beadingadjacent its proximal end and said plunger includes a second annularbeading on its inside surface adjacent said distal end of said plunger,wherein on manual withdrawal of said plunger in the proximal directionsaid second annular beading on said plunger engages said first annularbeading on said gripping means allowing said gripping means andoperatively engaged said needle attachment means to be withdrawn intosaid barrel in the event that the vacuum retraction fails.
 9. A syringecomprising:an elongated barrel having a proximal end and a distal end; ahollow plunger having a closed proximal end protruding from saidproximal end of said barrel and a distal end located within said barrel,and plunger being slidably mounted in said barrel and having a vacuum inits interior; a retractable needle attachment member for supporting ahypodermic needle; catch means for releasably holding said needleattachment member at said distal end of said barrel, said catch meansincluding at least one finger on said needle attachment member biasedinto engagement with portion of the interior of said barrel; grippingmeans for gripping and withdrawing said needle attachment member, saidgripping means closing said distal end of said plunger and having aplurality of retaining and gripping members cooperable with the distalend of said plunger for retaining said gripping means at said distal endof said plunger; and abutment means on a side wall of said barrel in thepath of movement of said gripping members, whereby when said plunger isadvanced and said gripping means approaches said needle attachmentmember, said abutment means is engaged by said retaining and grippingmembers of said gripping means and urges said gripping members inwardlyto reduce the radial dimensions of said gripping means and thusdisengages said gripping means from said distal end of said plunger, andwherein at least one said retaining and gripping member on said inwardmovement engages and deflects said at least one finger to release saidcatch means and permit said needle attachment member to be withdrawn bysaid gripping means into the interior of said plunger by the vacuumwithin said plunger.
 10. A syringe according to claim 9 wherein saidabutment means comprises an annular shoulder on an internal side wall ofsaid barrel.
 11. A syringe according to claim 9 wherein said fingerincludes a projection and wherein said portion of said barrel includesan annular recess on an internal side wall of said barrel which receivessaid projection on said finger.
 12. A syringe according to claim 11wherein said needle attachment member includes a plurality ofcircumferentially spaced said fingers and wherein said retaining andgripping members of said gripping means are engageable with respectivesaid fingers.
 13. A syringe comprising:an elongated barrel having aproximal and a distal end and a cylindrical side wall; a hollow tubularplunger having a closed proximal end protruding from said proximal endof said barrel and a distal end located within said barrel, said distalend having an annular end surface, said plunger being slidably mountedin said barrel and having a vacuum in its interior; a retractable needleattachment member for supporting a hypodermic needle; catch means forreleasably holding said needle attachment member at said distal end ofsaid barrel, said catch means including catch members on said needleattachment member cooperable with an annular recess in said cylindricalwall of said barrel; gripping means for gripping and withdrawing saidneedle attachment member, said gripping means closing said distal end ofsaid plunger and having a plurality of gripping members, said grippingmembers cooperating with said annular end face of said plunger to retainsaid gripping means at said distal end of said plunger, said grippingmembers further including camming means for causing deflection of saidgripping members; and an abutment shoulder on said side wall of saidbarrel in the path of movement of said gripping members towards saiddistal end of said barrel, whereby when said plunger is advanced andsaid gripping means approaches said needle attachment member, saidabutment shoulder is engaged by said camming means of said grippingmembers to cause said gripping members to be urged inwardly to disengagesaid gripping means from said distal end face of said plunger, and saidabutment shoulder further causing said gripping members on said inwardmovement to engage and deflect said catch members to release said catchmeans and permit said needle attachment member to be withdrawn by saidgripping means into the interior of said plunger by the vacuum withinsaid plunger.